Enhanced pilot signal receiver

ABSTRACT

Briefly, in accordance with one embodiment, a method of adjusting for digital automatic gain control (DAGC) quantization error in a mobile station is as follows. A first DAGC value is stored before reception of one or more enhanced pilot signals. A second DAGC value is computed during reception of the one or more enhanced pilot signal. The first DAGC value is restored after reception of the one or more enhanced pilot signals is over. An advantage associated with this particular embodiment may include reduction in quantization error for digital automatic gain control.

RELATED PATENT APPLICATIONS

This patent application is a divisional that claims priority to U.S.patent application Ser. No. 12/113,903, entitled “Enhanced Pilot SignalReceiver,” filed on May 1, 2008, which claims the benefit of: U.S.Provisional Patent Application Ser. No. 60/939,035, filed on May 18,2007; U.S. Provisional Patent Application Ser. No. 60/978,068, filed onOct. 5, 2007; U.S. Provisional Patent Application Ser. No. 61/014,706,filed on Dec. 18, 2007; U.S. provisional patent application Ser. No.61/038,660, filed on Mar. 21, 2008; U.S. Provisional Patent ApplicationSer. No. 61/016,101, filed on Dec. 21, 2007; all of the foregoingassigned to the assignee of currently claimed subject matter and hereinincorporated by reference in their entirety. Furthermore, the parentapplication to this divisional application, U.S. patent application Ser.No. 12/113,903 noted above, was concurrently filed with U.S. patentapplication Ser. No. 12/113,900, titled “Enhanced Pilot Signal”, filedon May 1, 2008, by Wu et al. (Attorney Docket No. 071317); and U.S.patent application Ser. No. 12/113,812, titled “Position Location forWireless Communications System”, filed on May 1, 2008, by Attar et al.(attorney docket no. 071421); both of which are assigned to the assigneeof currently claimed subject matter and incorporated by reference intheir entirety.

FIELD

This disclosure relates to receivers for use in wireless communicationsor other systems, such as receivers for enhanced pilot signals.

BACKGROUND

Mobile stations or other receivers, such as, for example, cellulartelephones, are beginning to include the ability to gather informationthat provides the ability to estimate position of the mobile station orother receiver. To have this capability, a mobile device, for example,may receive signals from a satellite positioning system (SPS), such as,for example, a Global Positioning System (GPS). Such information,perhaps in conjunction with other received information, may be employedto estimate position location. A variety of scenarios in which a mobilestation or receiver may estimate position location are possible.

However, for a variety of reasons, a mobile station may encounterdifficulties in receiving signals. For example, difficulties may beexperienced if the mobile station is positioned inside of a building, orin a tunnel, etc. In other circumstances, a mobile station may notinclude an SPS receiver. Again, a variety of scenarios are possible.However, due at least in part to difficulties related to the ability ofa mobile station to receive signals enabling it to estimate positionlocation, a need exists for alternate ways for a mobile station or otherdevice to estimate position location.

SUMMARY

Briefly, in accordance with one embodiment, a method of adjusting fordigital automatic gain control (DAGC) quantization error in a mobilestation is as follows. A first DAGC value is stored before reception ofone or more enhanced pilot signals. A second DAGC value is computedduring reception of the one or more enhanced pilot signal. The firstDAGC value is restored after reception of the one or more enhanced pilotsignals is over. An advantage associated with this particular embodimentmay include reduction in quantization error for digital automatic gaincontrol.

BRIEF DESCRIPTION OF THE FIGURES

Non-limiting and non-exhaustive embodiments are described herein withreference to the following figures:

FIG. 1 is a schematic diagram illustrating an embodiment employing threetime slots reuse scheme for enhanced pilot signaling;

FIG. 2 is a schematic diagram of an embodiment of a slot of a timedivision multiplexed signal transmission, such as may be employed in1xEV-DO, for example, to implement enhanced pilot signaling;

FIG. 3 is a schematic diagram illustrating an embodiment employing ninetime slots for enhanced pilot signaling;

FIG. 4 is a table associated with the embodiment shown in FIG. 3;

FIG. 5 is a schematic diagram illustrating an embodiment of a mobilestation; and

FIG. 6 is a schematic diagram illustrating an embodiment of a system forprocessing signals.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, methods, apparatuses or systems that would be known by one ofordinary skill have not been described in detail so as not to obscureclaimed subject matter.

Reference throughout this specification to one implementation, animplementation, one embodiment, an embodiment, or the like may mean thata particular feature, structure, or characteristic described inconnection with a particular implementation or embodiment may beincluded in at least one implementation or embodiment of claimed subjectmatter. Thus, appearances of such phrases in various places throughoutthis specification are not necessarily intended to refer to the sameimplementation or to any one particular implementation described.Furthermore, it is to be understood that particular features,structures, or characteristics described may be combined in various waysin one or more implementations. In general, of course, these and otherissues may vary with the particular context. Therefore, the particularcontext of the description or usage of these terms may provide helpfulguidance regarding inferences to be drawn for that particular context.

Likewise, the terms, “and”, “and/or”, and “or” as used herein mayinclude a variety of meanings that will, again, depend at least in partupon the context in which these terms are used. Typically, “and/or”, aswell as “or” if used to associate a list, such as A, B or C, is intendedto mean A, B, or C, here used in the exclusive sense, as well as A, Band C. In addition, the term “one or more” as used herein may be used todescribe any feature, structure, or characteristic in the singular ormay be used to describe some combination of features, structures orcharacteristics.

Some portions of the detailed description which follow are presented interms of algorithms or symbolic representations of operations on databits or binary digital signals stored within a computing system memory,such as a computer memory. These algorithmic descriptions orrepresentations encompass techniques used by those of ordinary skill inthe data processing or similar arts to convey the substance of theirwork to others skilled in the art. An algorithm is here, and generally,considered to be a self-consistent sequence of operations and/or similarprocessing leading to a desired result. The operations and/or processinginvolve physical manipulations of physical quantities. Typically,although not necessarily, these quantities may take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared or otherwise manipulated. It has proven convenient,at times, principally for reasons of common usage, to refer to thesesignals as bits, data, values, elements, symbols, characters, terms,numbers, numerals or the like. It should be understood, however, thatall of these or similar terms are to be associated with the appropriatephysical quantities and are intended to merely be convenient labels.Unless specifically stated otherwise, as apparent from the followingdiscussion, it is appreciated that throughout this specification,discussions utilizing terms such as “processing”, “computing”,“calculating”, “determining” or the like refer to the actions orprocesses of a computing platform, such as a computer or a similarelectronic computing device, that manipulates or transforms datarepresented as physical electronic or magnetic quantities, or otherphysical quantities, within the computing platform's memories,registers, or other information storage, transmission, or displaydevices.

As previously indicated, a need exists for ways of estimating positionlocation for a mobile station or other device. Although receivingsatellite signals, as previously indicated, provides one approach, otherapproaches that may either supplement such signals or be employedinstead of such an approach remain desirable.

In this context, the term mobile station is meant to refer to any devicehaving the ability to receive wireless signals and send wirelesssignals, which is also capable of being mobile with respect to positionlocation. A mobile station typically will receive signals in connectionwith usage as part of a wireless communications system. Furthermore,also typically, but not necessarily, a mobile station may communicatewith one or more cells in a wireless communication system. Typically,such cells may comprise base stations. Therefore, it may be desirablefor information gathered via base station communications to be utilizedby a mobile station, sometimes referred to as a mobile, in estimatingposition location. Likewise, as indicated above, such information maysupplement information available through other mechanisms, such as viasatellite or via a position determining entity (PDE), for example.

However, a mobile station in communication with one or more basestations to gather information may encounter difficulties in somecircumstances due to, for example, interference. For example,interference may occur between signals transmitted by several basestations. Thus, in this example, a mobile station may not be able toadequately communicate with one or more of the base stations, resultingin an inability or a reduced ability to perform an accurate positionlocation estimate. This is sometimes referred to as the “hearabilityproblem” due at least in part to the “near-far effect”. For example, forwireless communications systems, such as cdma2000 and WCDMA, to providewithout limitation only a few possible examples, downlink pilot signalsmay be difficult to detect due at least in part to such interference

Although claimed subject matter is not limited in scope to anyparticular embodiment, in a variety of example embodiments, an approachto signal communications may be discussed to address at least in partthe issues discussed above. In descriptions of such example embodiments,aspects of the signaling may relate to the time domain, the frequencydomain or to other aspects of a particular signal, referred to here assignal dimensions. Nonetheless, it is intended that claims subjectmatter not be limited in scope to signaling in these example domains orsignal dimensions. These examples are merely illustrative. For example,in other embodiments, instead of time or frequency, other dimensions ofa signal may be involved, such as, for example, phase, amplitude,spreading code or spreading code sequence, signal energy or anycombinations thereof. In this context, the term signal dimension isintended to refer to a quantifiable aspect of a signal that may varyacross a variety of signals and that may be used to categorize orpartition signals which vary from one another in this particularquantifiable aspect. A signal, for example, may occupy time andfrequency domain resources simultaneously. As described in some of theembodiments below, a scheme may be employed to divide these resourcesinto orthogonal dimensions: in time domain, in frequency domain, infixed time and frequency domain, or code domain, to provide someexamples. Claimed subject matter is not intended to be limited to thespecific example embodiments discussed. Rather, many other signalingtechniques or signaling approaches that employ other signal dimensionsare included within the scope of claimed subject matter. It is intendedthat the scope of claimed subject matter include all such techniques andapproaches.

In one particular embodiment of a method of transmitting signals, forexample, signal waveforms may be transmitted from at least tworespective sectors of a wireless communications system. The at least tworespective sectors, likewise, may be from at least two different sets ofa superset of sectors. For example, a superset of sectors, such asillustrated in FIG. 1, as an example, may be divided into at least two,and as illustrated in FIG. 1, in some embodiments, more than two sets ofsectors. Thus, in this particular embodiment, the sectors transmittingsignals may be from separate sets of sectors. Likewise, in thisparticular embodiment, the signal waveforms transmitted may be at leastnearly mutually orthogonal, at least along a particular signaldimension, such as, for example, time or frequency, as shall bediscussed below in more detail.

FIG. 1, for example, illustrates an embodiment in which a superset ofsectors are partitioned or divided into 3 sets, S0, S1, and S2,although, of course, claimed subject matter is not limited in scope inthis respect. The spatial arrangement of sectors is illustrated by 110and the particular time slots in which those sectors may transmitenhanced pilot signals is illustrated by 120. As indicated above, thisapproach could be applied to a variety of signal dimensions, such as,for example time and/or frequency, to provide only two out of more thantwo possible examples. However, for ease of explanation, we shallillustrate an example embodiment for the protocol 1xEV-DO, which employsuplink and downlink signal transmissions in which information is slottedinto various time slots.

Protocol 1xEV-DO is part of a family of CDMA2000 1x digital wirelessstandards. 1xEV-DO is a third generation or “3G” CDMA standard. Thereare currently two main versions of 1xEV-DO: “Release 0” and “RevisionA”. 1xEV-DO is based on a technology initially known as “HDR” (High DataRate) or “HRPD” (High Rate Packet Data), developed by Qualcomm. Theinternational standard is known as IS-856.

FIG. 2 is one possible example embodiment 210 of a time divisionmultiplexed (TDM) signal that may employ enhanced pilot signaling,although, of course, claimed subject matter is not limited in scope tothis particular example. Embodiment 210 is intended to illustrate oneenhanced pilot signal slot. In the 1xEVDO downlink, a Pilot Channel istime division multiplexed with other channels. The Pilot Channel in thisexample, is designated by 210-250. A 1xEV-DO downlink transmissionincludes time slots of length 2048 chips. Groups of 16 slots align withan offset pseudo-random noise or PN sequence. As illustrated by 210,within a slot, Pilot, enhanced media access control (MAC) and Traffic orControl Channels are time division multiplexed. Thus, for an embodimentof enhanced pilot signaling for a 1xEV-DO downlink, time slots may beallocated for enhanced pilot signals. Here, FIG. 2 illustrates onepossible embodiment of such a slot structure, although, for course,claimed subject matter is not limited in scope to this example. Manyother possible enhanced pilot signal configurations or structures arepossible and are included within the scope of claimed subject matter.

For this embodiment, however, enhanced pilot channels or signals aretransmitted in the data portion of these dedicated slots, while legacyPilot and MAC channels are retained for backward comparability. For thisembodiment, the enhanced pilot may appear as an unintended packet forlegacy mobile stations, for example, that would not have the ability torecognize it. Likewise, for this embodiment, this slot may betransmitted with a relatively low “duty cycle”, such as around 1% andstill provide signaling benefits. In this way, potential impact ondownlink capacity may not be significant.

An aspect of embodiments in accordance with claimed subject matter, suchas the embodiment just discussed, relates to so-called “reuse”. Thisterm refers to the concept that signaling resources, such as frequencybandwidth or signal duration, for example, that may be available in aparticular signaling dimension (or in several signaling dimensions insome embodiments) may be employed (or reemployed) by other or differentsectors. For example, in the embodiment described above, dedicated timeslots may be partitioned to correspond, for example, to the sets ofsectors illustrated in FIG. 1. In this example, 3 non-overlappingpartitions have been formed, although claimed subject matter is notlimited in scope in this respect. Any number of groups, referred to hereas K or as reuse factor 1/K may be employed and the sectors are notrequired to be non-overlapping. However, regardless of the details ofthis particular embodiment, a one-to-one association, by construction,may exist between the partitions of the dedicated time slots and thepartitions of the sets of sectors of the superset. Sectors of aparticular set may only transmit enhanced pilot signals in itsassociated slots. This is referred to as reuse over time, here, since inthis embodiment signaling resources available along the time signalingdimension have been partitioned to correspond to the partitioned sets ofsectors that together comprise the superset of sectors.

One advantage of the approach of this particular embodiment, assuggested previously, relates to a reduction in signal transmissioninterference. In other words, by partitioning sectors along a signaldimension so that the transmitted signal waveforms are nearly mutuallyorthogonal results in pilot signals that are more easily detected by amobile station, for example.

Partitioning of sectors or cells for ease of discussion may be referredto here as “coloring”, although the use “colors” is, of course, not anecessary feature of claimed subject matter or even of this particularembodiment. Rather, the term “color” is intended here to identifypartitions or partitioning. Thus, as described in more detailimmediately below, “color” here, which merely designates a partition,which for a sector, for example, refers to a 2tuple, rather than theconventional notion of color. For example, and without limitation, if welet a cell take on a value from the set {Red, Green, Blue} (abbreviatedas {R, G, B}), a sector may, in this example, take on a value from theset {R, G, B}x{α, β, γ}, where “x” stands for Cartesian product. Thus,in this example, the “color” of the cell influences the “color” of thesectors of that cell. Of course, it is appreciated that claimed subjectmatter is not necessarily restricted to partitioning by cells orsectors. For example, in alternative embodiments, other subdivisions orpartitions may be employed. However, as indicated above, the color of asector may be referred to as a 2tuple, for example (R, α) abbreviated asRα, the first element, again, coming from the color of the cell to whichthe sector belongs. Based at least in part on the discussion above, itshould now be apparent that the reuse factor for this particular exampleis K=9 or 1/9.

An example embodiment 310 is shown in FIG. 3 that differs from theembodiment shown in FIG. 1. FIG. 3 also illustrates an example ofplanned or dedicated coloring. For the particular embodiment beingdiscussed, transmitted signal waveforms comprise time divisionmultiplexed (TDM) signal waveforms, as illustrated by 410 in FIG. 4. Inplanned coloring, colors are assigned in a fixed or dedicated manner soas to reduce interference among sectors of the same color in a balancedway, although, of course, claimed subject matter is not limited in scopeto employing such an approach. Thus, as is illustrated by FIGS. 3 and 4,signals are transmitted in particular time slots so that potentialsignal interference is reduced. As may now be appreciated from the abovediscussion, dedicated resource and reuse reduces inter-channelinterference, and thus assists to mitigate the near-far effect andlikewise improve hearability. Therefore, for this particular embodimentat least, the TDM signal waveforms that are transmitted in dedicatedtime slots associated with particular cell sectors comprise highlydetectable pilot (HDP) signals. As shall be discussed further below,this allows for improved terrestrial position location estimationaccuracy, although, again, claimed subject matter is not limited inscope in this respect.

While dedicated or planned coloring provides potential advantages someof which are discussed above, color assignment to reduce theinterference among sectors of the same color in a balance a way wouldinvolve some amount of effort. If it were possible to reduce or avoidthis effort, it may, in some situations, provide advantageous. Oneapproach may be to employ what may be referred to here as time varyingcoloring, rather than dedicated coloring. In time varying coloring, thecolor of various sectors may change with time. One particular example oftime varying coloring described in more detail below is referred to hereas random coloring. In random coloring, again, the color of varioussectors may change; however, the changes are a pseudo-random. Thus, inrandom coloring, the color of a sector varies with time in apseudo-random manner, where here, again, with respect to a sector, theterm color refers to a 2tuple, as discussed previously. For example,assume, as previously, that enhanced pilot signals are time-multiplexedinto 9 time slots to correspond with 9 sets or groupings of sectors thattogether form a superset, as previously discussed.

As previously described, enhanced pilot channels or signals may betransmitted and provide the ability for greater accuracy in makingposition location estimates of the mobile station if such signals arereceived by a mobile station or other receiver. However, a factor indetermining whether improved accuracy will be realized depends in atleast in part on the ability of the mobile station or other receiver todetect the signals and likewise, process them in such a manner thatprovides the desired accuracy. Therefore, aspects of the configurationof the receiver of the mobile station or other device may have relevancein connection with position location estimation by the mobile station.

Although there are many aspects of receivers, here, a few specific areasof a configuration of a receiver portion of a mobile station areconsidered so that advantages afforded by the use of enhanced pilotsignals will be realized in operation. In this context, it is desirableto highlight features that may be included to take advantage of acommunications system, for example, in which enhanced pilot signals areavailable. However, claimed subject matter is not limited in scope toparticular embodiments. Therefore, while specific embodiments arediscussed to illustrate various potential feature enhancements, claimedsubject matter is intended to be conceptually much broader than thespecifics associated with the embodiments discussed below.

One aspect of a receiver of a mobile station to consider in connectionwith improved estimates of position location is sources of receiverquantization error. For example, in an example wireless communicationssystem, such as one that may employ 1xEV-DO, as discussed above, widevariations may be observed in received signal energy, depending at leastin part upon whether the DO pilot signal is being received or anenhanced pilot signal is being received. As discussed, enhanced pilotsignals employ reuse, which has the potential to reduce signal energy.As simple one example, if K=9 is the reuse factor, then the signalenergy for enhanced pilot signals may be about an order of magnitudeless than that of the DO pilot. However, to the extent these receivedsignals become quantized, significant variations in level may result inincreased quantization error due to a relatively large range of possiblesignal levels. More specifically, an automatic gain control or AGC loopis frequently employed to convert a received signal into a voltagelevel. Likewise, for processing purposes, the voltage signal level isconverted from an analog signal to a digital signal. However, aspreviously suggested, wide variations in the received signal maycontribute to higher levels of quantization error which may ultimatelyresult in signal quality degradation or signal accuracy degradation.

Another aspect to consider is sources of signal interference. An aspectof employing enhanced pilot signals is to reduce interference fromnearby base stations that may be transmitting interfering pilot signals.However, other potential sources of interference likewise exist. Anotherpotential source of signal interference for example, may result fromadjacent channels other than pilot signals. For example, for 1xEV-DO,bandwidth for a pilot channel is 1.25 MHz. This bandwidth issufficiently narrow that nearby carrier signals transmitting at the sametime may have signal energy at frequencies that overlap with the pilotsignal, potentially resulting in interference. Such interference,therefore, may affect hearability and, in this respect, is similar tothe near-far effect, discussed previously with respect to enhanced pilotsignals.

Yet another aspect of a receiver of a mobile station to consider relatesto having adequate time to perform signal processing. Computing alocation position estimate is a relatively complex computation in termsof the operations to be performed. With respect to employing enhancedpilot signals, a large number of signal thresholds are computed due atleast in part to the number of transmitting sectors. It is possible thatthere may not be sufficient time available to perform such calculationsor operations for every sector transmitting enhanced pilot signals. Ifthis is the case, it may be desirable to have a mechanism to limit thenumber of enhanced pilots for which signal detection is performed sothat the number of calculations and, as a result, the amount of time toperform signal processing, is reduced.

As previously discussed, wide variations in received signal energy hasthe potential to affect performance of an AGC loop, particularly if A/Dconversion is also employed. Thus, as previously indicated errorsarising from quantization of an analog signal may have the potential toaffect the quality of a position location estimate. One possibleapproach to addressing an issue such as this may involve a change orupgrade in the base computing device or platform employed. For example,an increase in the number of bits used to quantize the signal shouldreduce quantization error. However, for a variety of reasons, it may beviewed as desirable to employ a similar platform to the one employed inconnection with processing pilot signals that have not been enhanced,such as, for example, the DO pilot signal provided in compliance withthe 1xEV-DO specification, as simply one example. Advantages of thisapproach may include reduced cost or reduced complexity. Increasing thenumber of bits may increase either or both. Likewise, it should bedesirable to not introduce significant additional computationalcomplexity even assuming a similar platform is employed. Again, assuggested previously, increasing the time to perform signal processingmay be undesirable in some instances at least.

Assuming, as just indicated, that the platform employed to processenhanced pilot signals is similar or substantially the same as theplatform, several possible signal processing approaches remain availableto address some of the issues discussed above. As shall be discussed inmore detail below, one option in accordance with claimed subject mattermay include employing a “window” in which enhanced pilots signals may bereceived and performing AGC operations based at least in part on theenhanced pilot signals received during such a window. Another option,while employing a similar platform as employed for non-enhanced pilotsignals, may involve the use of separate AGC loops. For example, two AGCloops may be implemented without significant platform modifications. Asshall become clear from the discussion below, to do this, it isdesirable to be able to execute signal processing operations atappropriate times with respect to received enhanced pilot signals.

Although claimed subject matter is not limited in scope to thisparticular embodiment, in one embodiment, a method of reducing digitalAGC quantization error in a mobile station may include the following.Signal energy from one or more received enhanced pilot signals may beestimated. A portion of an analog to digital (A/D) converted signallevel value may be selected as a digital AGC value based at least inpart on the foregoing estimate. Likewise, one or more enhanced pilotsignal thresholds may be scaled to at least approximately to adjust forsignal processing applied to reduce quantization error.

Signal energy may, for example, be estimated by integrating, over aperiod, of time I and Q components of received enhanced pilot signals.Although claimed subject matter is not limited in scope in this respect,in one particular embodiment, all six bits of an output signal of asix-bit A/D converter may not necessarily be entirely employed in theAGC loop computations. For example, this may reduce computationalcomplexity, although potentially at the risk of less precision; however,as described below, for an embodiment in accordance with claimed subjectmatter, precision may be accommodated without resorting to use of allsix bits. As an example, without limitation, in one possible embodiment,four bits of the A/D converter may be selected to be provided for use inperforming threshold detection.

In this particular embodiment, for example, an estimate of signal energyfor one or more received enhanced pilot signals is performeddynamically. Typically, the most significant bits, such as the four mostsignificant bits, for example, might be provided, such as in the case ofa DO pilot, for example. However, for enhanced pilot signaling, thereceived energy should be relatively low due at least in part to thereuse factor, 1/K. In a situation such as this, if the most significantbits are provided, information may be lost that maybe useful, since moreinformation may be contained in the lesser significant bits. Forexample, if the energy of the enhanced pilot signal is relatively low,such as one the order of 20 dB below regular DO pilot energy. It maybedesirable to provide the four least significant bits. However, asalluded to above, since this might be viewed as equivalent to shifting abinary signal by several places, it may be appropriate to compensate forchanges intended to reduce quantization error, such as shifting aquantized measurement, through other adjustments in the computations.For example, one approach may be to proportionately scale values orthresholds used to determine whether the level of signal detected isstatistically significant. Although claimed subject matter is notlimited in scope in this respect, signal levels for one or more receivedenhanced pilot signals may, for example, be around an order of magnitudeless than signal levels for one or more non-enhanced pilot signals, suchas, for example, the DO pilot signal received in connection with the1xEV-DO signaling protocol.

As previously suggested, another possible approach may involveimplementing two AGC loops, one for enhanced pilot signals and one fornon-enhanced pilot signals. This approach has the advantage that it maybe implemented without significant platform modifications. To do thiseffectively, however, it is desirable to be able to execute signalprocessing operations at appropriate times with respect to receivedenhanced pilot signals. For example, although claimed subject matter isnot limited in scope in this respect, referring to an AGC loop for amobile station, the energy of the signal wave front may be accumulatedover a number of chips, such as 40 to 60, as only one potential example,and thereafter, the loop may update the estimate at regular intervals ofchips, if desired. In contrast, for the AGC loop for the enhanced pilotsignal, such energy may be captured once per enhanced pilot burst, whichfor the embodiment previously described, occurs relatively infrequently,such as about 1% of the time. Therefore, smoothly switching between AGCloops and doing so at appropriate times is desirable.

As previously described, another aspect of potential performanceimprovement relates to interference from an adjacent channel. Ingeneral, although other channels other than enhanced pilot signals maybe transmitted over a different carrier, leakage may occur inoverlapping frequencies among the various channels, potentiallyaffecting performance. More specifically, degradation may be observedthrough a lower signal to noise ratio, as one example. This phenomenonis similar to the near-far problem, and thus may affect hearability, aspreviously described. It is noted likewise, that this effect may notaffect all implementations of enhanced pilot signaling. For example, forOFDM systems, in which enhanced pilot signaling may be employed, theamount of available bandwidth is greater, so that interference fromadjacent channels may have a barely measurable impact on performance. Incontrast, however, for time division multiplexed signals, such as in1xEV-DO, for example, the allotted bandwidth is 1.25 megahertz, makingsignal degradation from interference is more likely.

Although claimed subject matter is not limited in scope in this respect,in accordance with one particular embodiment, a notch filter may beapplied to received enhanced pilot signal transmissions. As previouslysuggested, the enhanced pilot signal transmissions from different setsof sectors are mutually orthogonal at least along a time signaldimension, since they are TDM signals. In this embodiment, for example,the notch filter may have a notch at a frequency corresponding to thesignal transmissions for the adjacent potentially interfering channels.It is noted, of course, that a host of possible implementations arepossible and claimed subject matter is not limited in scope to anyparticular one. For example, an FIR or an IRR filter may be employed.

Likewise, the filtered signals may be employed to perform automatic gaincontrol. It is worth observing that a notch filter may removeinterference from adjacent channels, but it likewise may undesirablyincrease inter-symbol interference for the enhanced pilot signals. Onepossible approach to address this, although adding complexity, would beto vary the specific application of the notch filter so that signals arenot unnecessarily degraded by its application if there is littleinterference attributable to adjacent channel transmissions. In thisparticular embodiment, however, because, again, reduced complexity ofsignal processing is desired, instead, filtering is always applied toenhanced pilot signals before employing automatic gain control. Thisapproach offers simplicity of implementation without significantlyaffecting performance. For sectors providing weak enhanced pilot signalsto the mobile station, interference attributable to adjacent channeltransmissions may be greater than potential inter-symbol interferencethat the filter may induce. However, for sectors providing strongenhanced pilot signals to the mobile station, the effect of inter-symbolinterference from application of filtering is sufficiently small so asnot to significantly degrade performance.

As previously suggested, another aspect related to the receiverconfiguration for a mobile station involves having sufficient time toprocess enhanced pilot signaling that may be received. As suggestedpreviously, there may not be sufficient time to process signals fromevery sector transmitting enhanced pilot signals. Therefore, an approachis desired to reduce the number of enhanced pilot signals that a mobilestation is to process. If the mobile station is able to omit processingthose signals that are less likely provide an accurate estimate ofposition location, this has the potential to reduce processing time toan acceptable period of time.

One particular embodiment in accordance with claimed subject matter thatmay permit the mobile station to not process signals less likely toprovide an accurate position location estimate may involve providing tomobile station with information about the particular enhanced pilotsignaling transmission scheme. For example, with limitation, in oneembodiment, this information may be loading in memory of the mobilestation before the mobile station is deployed. In another embodiment,perhaps this information is transmitted to the mobile station. Themobile station may then use this information to detect enhanced pilotsignals for those sectors of interest while omitting sectors that arenot of interest.

For example, again, but without limitation, suppose a particularcommunication system employs an embodiment of enhanced pilot signalsthat includes dedicated “coloring”, as previously described. For ease ofdiscussion, assume this system also employs time multiplexed signals,although, as previously indicated, many other approaches may beemployed, such as FDM, OFDM, etc. In this particular embodiment,however, enhanced pilot signals may be detected for selected time slotscorresponding to sectors of interest to reduce the amount of signalprocessing and, therefore, the time to complete the signal processing.

Of course, alternatively such a system may employ a non-dedicatedscheme, such as a random or time-varying scheme. In such an embodiment,it may be more complex for the mobile station to determine those slotsto detect and those to omit. However, it remains possible to reduce thenumber of enhanced pilot signals to be processed, as desired. Forexample, in a non-dedicated scheme employing random coloring, apseudo-random process is employed to make associations betweenparticular sectors and time slots, for this particular embodiment, forexample. If the mobile station has the particular pseudo-random processand the initial seed, for example, it may determine the association.Thus, enhanced pilot signals may be detected based on selected timeslots corresponding to sectors of interest, as before. Of course, asimilar approach may likewise be employed in an embodiment in which theenhanced pilot signals are FDM signals, for example. Again, by applyingthe same pseudo-random process starting with the same seed, for example,the mobile station is able to determine the selected frequenciescorresponding to selected sectors of interest and check thosefrequencies as part of a signal detection process, thereby reducingprocessing to perform such computations.

Similar to non-enhanced pilot signals, enhanced pilot signals may beencoded using a pseudo-random (PN) sequence. In one embodiment, forexample, so that non-enhanced pilot signals and enhanced pilot signalsare not confused, a frequency inverted PN sequence, which comprises acomplex conjugate, may be employed. However, this approach torandomizing the enhanced pilot signals may also be employed as amechanism to identify those signals to which signal detection is to beapplied. Different signals from different sectors or base stations willbe coded with a different PN sequence. Thus, by locally generating thePN sequence employed to encode the signals of interest, for example, amobile station may attempt to decode received signals, looking for amatch. If there is a match, the decoded signals may be processed by themobile station and the enhanced pilot signals may be employed toestimate position location for the mobile station. Alternatively, ifthere is not a match, then the mobile station may continue to correlatethe PN sequence with received signals until a match occurs.

As alluded to previously, in some embodiments, a hybrid approach toposition location may be employed. For example, while an enhanced pilotsignal may be employed as part of a wireless communications system, itmay be supplemented with other information available via signalsreceived through other mechanism to determine position location, such aspseudorandom measurements to space vehicles that may be obtained byprocessing SPS signals. Likewise, determining a position locationestimate need not be performed entirely at the mobile unit. It may, forexample, include transmitting location information to an outside entity(e.g., a position determination entity).

As previously discussed, enhanced pilot signals may be provided in manyforms, such as time segments, frequency bands, or time-frequency bins.In any of these latter examples, partitioning into K groups along one ormore signaling dimensions, such as time, frequency, or time-frequency,for example, may be applied so that the partitions are orthogonal ornearly so. Likewise, a superset of sectors may also be partition into Ksets or groups. As discussed previously with reference to a particularembodiment, a one-to-one association may be established between theorthogonal or nearly orthogonal partitions and the sector partitions. Insuch an embodiment, for a particular set of sectors, an enhanced pilotsignal may be transmitted with the particular window of the particularone or more signaling dimensions that have been partitioned. Likewise,as discussed previously with reference to a particular embodiment,dedicated coloring or time varying coloring, such as random coloring,may be applied. Therefore, as has been previously discussed andillustrated with respect to particular embodiments, enhanced pilotsignaling may be applied to OFDM systems, such as WiMax, LTE, UMB, orother 4G approaches being developed, for example, by 3GPP or 3GPP2. Ofcourse, again, these are examples and claimed subject matter is intendedto cover more than OFDM systems as well.

Therefore, wireless communication or position location estimationtechniques, such as, for example, the embodiments previously described,may be used for a host of various wireless communication networks.Without limitation, these may include Code Division Multiple Access(CDMA) networks, Time Division Multiple Access (TDMA) networks,Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA(OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, etc. A CDMAnetwork may implement one or more radio access technologies (RATs) suchas cdma2000, Wideband-CDMA (W-CDMA), or Universal Terrestrial RadioAccess (UTRA), to name just a few radio technologies. Here, cdma2000 mayinclude technologies implemented according to IS-95, IS-2000, or IS-856standards. UTRA may include Wideband-CDMA (W-CDMA) or Low Chip Rate(LCR). A TDMA network may implement a radio technology such as GlobalSystem for Mobile Communications (GSM). An OFDMA network may implement aradio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part ofUniversal Mobile Telecommunication System (UMTS). Long Term Evolution(LTE) is an upcoming release of UMTS that may use E-UTRA. UTRA, E-UTRA,GSM, UMTS and LTE are described in documents that may be obtained fromthe 3rd Generation Partnership Project (3GPP). Cdma2000 is described indocuments that may be obtained from the 3rd Generation PartnershipProject 2 (3GPP2). 3GPP and 3GPP2 documents are, of course, publiclyavailable.

An example implementation of a system for processing signals isillustrated in FIG. 6. However, this is merely an example of a systemthat is capable of acquiring signals by processing according to aparticular example and other systems may be used without deviating fromclaimed subject matter. As illustrated in FIG. 6, according to thisparticular example, such a system may comprise a computing platformincluding a processor 1302, memory 1304, and correlator 1306. Correlator1306 may produce correlation functions or operations for signalsprovided by a receiver (not shown) to be processed by processor 1302,either directly or through memory 1304. Correlator 1306 may beimplemented in hardware, firmware, software, or any combination.However, this merely an example of how a correlator may be implementedand claimed subject matter is not limited to this particular example.

Here, however, continuing with this example, memory 1304 may storeinstructions which are accessible and executable by processor 1302.Here, processor 1302 in combination with such instructions may perform avariety of the operations previously described, such as, for example,without limitation, correlating a PN or other sequence.

Turning to FIG. 5, radio transceiver 1406 may modulate a radio frequency(RF) carrier signal with baseband information, such as voice or data, ordemodulate a modulated RF carrier signal to obtain baseband information.Antenna 1410 may transmit a modulated RF carrier or receive a modulatedRF carrier, such as via a wireless communications link.

Baseband processor 1408 may provide baseband information from CPU 1402to transceiver 1406 for transmission over a wireless communicationslink. Here, CPU 1402 may obtain such baseband information from an inputdevice within user interface 1416. Baseband processor 1408 may alsoprovide baseband information from transceiver 1406 to CPU 1402 fortransmission through an output device within user interface 1416. Userinterface 1416 may comprise a plurality of devices for inputting oroutputting user information, such as voice or data. Such devices mayinclude, for example, a keyboard, a display screen, a microphone, or aspeaker.

Here, SPS receiver 1412 may receive and demodulate SPS transmissions,and provide demodulated information to correlator 1418. Correlator 1418may apply correlation functions from information provided by receiver1412. For a given PN sequence, for example, correlator 1418 may producea correlation function which may, for example, be applied in accordancewith defined coherent and non-coherent integration parameters.Correlator 1418 may also apply pilot-related correlation functions frominformation relating to pilot signals provided by transceiver 1406.Channel decoder 1420 may decode channel symbols received from basebandprocessor 1408 into underlying source bits. In one example in whichchannel symbols comprise convolutionally encoded symbols, such a channeldecoder may comprise a Viterbi decoder. In a second example, in whichchannel symbols comprise serial or parallel concatenations ofconvolutional codes, channel decoder 1420 may comprise a turbo decoder.

Memory 1404 may comprise computer readable media to store instructionswhich are executable to perform one or more of processes orimplementations, which have been described or suggested previously, forexample. CPU 1402 may access and execute such instructions. Throughexecution of these instructions, CPU 1402 may direct correlator 1418 toperform a variety of signal processing related tasks. However, these aremerely examples of tasks that may be performed by a CPU in a particularaspect and claimed subject matter in not limited in these respects. Itshould be further understood that these are merely examples of systemsfor estimating a position location and claimed subject matter is notlimited in these respects.

It will, of course, be understood that, although particular embodimentshave just been described, claimed subject matter is not limited in scopeto a particular embodiment or implementation. For example, oneembodiment may be in hardware, such as implemented to operate on adevice or combination of devices, for example, whereas anotherembodiment may be in software. Likewise, an embodiment may beimplemented in firmware, or as any combination of hardware, software,and/or firmware, for example. The methodologies described herein may beimplemented by various means depending upon the application. For ahardware implementation, the processing units may be implemented withinone or more application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,electronic devices, other electronic units designed to perform thefunctions described herein, or a combination thereof. For a firmwareand/or software implementation, the methodologies may be implementedwith modules (e.g., procedures, functions, and so on) that perform thefunctions described herein. Any machine readable medium tangiblyembodying instructions may be used in implementing the methodologiesdescribed herein. For example, software codes may be stored in a memory,for example, a memory of a mobile station, and executed by a processor,for example a microprocessor. Memory may be implemented within theprocessor or external to the processor. As used herein the term “memory”refers to any type of long term, short term, volatile, nonvolatile, orother memory and is not to be limited to any particular type of memoryor number of memories, or type of media upon which memory is stored.Likewise, although claimed subject matter is not limited in scope inthis respect, one embodiment may comprise one or more articles, such asa storage medium or storage media. This storage media, such as, one ormore CD-ROMs and/or disks, for example, may have stored thereoninstructions, that if executed by a system, such as a computer system,computing platform, or other system, for example, may result in anembodiment of a method in accordance with claimed subject matter beingexecuted, such as one of the embodiments previously described, forexample. As one potential example, a computing platform may include oneor more processing units or processors, one or more input/outputdevices, such as a display, a keyboard and/or a mouse, and/or one ormore memories, such as static random access memory, dynamic randomaccess memory, flash memory, and/or a hard drive.

In the preceding description, various aspects of claimed subject matterhave been described. For purposes of explanation, specific numbers,systems and/or configurations were set forth to provide a thoroughunderstanding of claimed subject matter. However, it should be apparentto one skilled in the art having the benefit of this disclosure thatclaimed subject matter may be practiced without the specific details. Inother instances, well known features were omitted and/or simplified soas not to obscure claimed subject matter. While certain features havebeen illustrated and/or described herein, many modifications,substitutions, changes and/or equivalents will now occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and/or changes asfall within the true spirit of claimed subject matter.

1. A method of adjusting for digital automatic gain control (DAGC)quantization error in a mobile station: storing a first DAGC valuebefore reception of one or more enhanced pilot signals; computing asecond DAGC value during reception of the one or more enhanced pilotsignal; and restoring the first DAGC value after reception of the one ormore enhanced pilot signals is over.
 2. The method of claim 1, wherein,for more than one received enhanced pilot signals, the enhanced pilotsignals are mutually orthogonal along at least one of the followingsignal dimensions: time, frequency, or any combination thereof.
 3. Themethod of claim 2, wherein the one or more enhanced pilot signals arecompatible with at least one of the following signaling protocols: 1xEV-DO; cdma2000; WiMAX; LTE; or UMB.
 4. The method of claim 1, andfurther comprising: selecting a portion of an analog-to-digitalconverted (ADC) value as a DAGC value for the first and second DAGCvalues.
 5. An article comprising: a storage medium having stored thereoninstructions that if executed direct a mobile station to store a firstDAGC value before reception of one or more enhanced pilot signals,compute a second DAGC value during reception of the one or more enhancedpilot signal, and restore the first DAGC value after reception of theone or more enhanced pilot signals is over.
 6. The article of claim 5,wherein, for more than one received enhanced pilot signals, the enhancedpilot signals are to be mutually orthogonal along at least one of thefollowing signal dimensions: time, frequency, or any combinationthereof.
 7. A mobile station comprising: a computing platform; saidcomputing platform to store a first DAGC value before reception of oneor more enhanced pilot signals, compute a second DAGC value duringreception of the one or more enhanced pilot signal, and restore thefirst DAGC value after reception of the one or more enhanced pilotsignals is over.
 8. The mobile of claim 7, wherein, for more than onereceived enhanced pilot signals, the enhanced pilot signals are to bemutually orthogonal along at least one of the following signaldimensions: time, frequency, or any combination thereof.
 9. A mobilestation comprising: means for storing a first DAGC value beforereception of one or more enhanced pilot signals; means for computing asecond DAGC value during reception of the one or more enhanced pilotsignal; and means for restoring the first DAGC value after reception ofthe one or more enhanced pilot signals is over.
 10. The mobile of claim9, wherein, for more than one received enhanced pilot signals, theenhanced pilot signals are mutually orthogonal along at least one of thefollowing signal dimensions: time, frequency, or any combinationthereof.